Abstract
Herein, elastomeric fibers that have shape memory properties due to the presence of a gallium core that can undergo phase transition from solid to liquid in response to mild heating are described. The gallium is injected into the core of a hollow fiber formed by melt processing. This approach provides a straightforward method to create shape memory properties from any hollow elastic fiber. Solidifying the core changes the effective fiber modulus from 4 to 1253 MPa. This increase in stiffness can preserve the fiber in a deformed shape. The elastic energy stored in the polymer shell during deformation drives the fiber to relax back to its original geometry upon melting the solid gallium core, allowing for shape memory. Although waxes are used previously for this purpose, the use of gallium is compelling because of its metallic electrical and thermal conductivity. In addition, the use of a rigid metallic core provides perfect fixity of the shape memory fiber. Notably, the use of gallium—with a melting point above room temperature but below body temperature—allows the user to melt and deform local regions of the fiber by hand and thereby tune the effective modulus and shape of the fiber.
Highlights
The use of metallic cores as a mechanism to retain elastic fibers in a temporary shape has several advantages relative toThis paper describes hollow elastomeric fibers with metallic conventional shape memory polymers: cores that can be programmed into stable, temporary shapes at room temperature
Gallium is a supercooled liquid metal at room temperature;[31] that is, it stays in the liquid state below its freezing point (29.8 °C)
This paper describes soft and stretchable, elastic shape memory fibers with electrical conductivity fabricated by injecting liquid gallium into elastic and hollow fibers
Summary
This paper describes hollow elastomeric fibers with metallic conventional shape memory polymers: cores that can be programmed into stable, temporary shapes at room temperature. The fibers here trigger a shape memory response above a single temperature: the melting point of the metal. The work here takes advantage of the fact body temperature is sufficient to melt the gallium core due to the low melting point of the metal (29.8 °C), enabling localized melting (and deformation) of the core using heat from fingers (for example). The fiber form-factor can create complex geometries via twisting and elongating and can undergo large deformation while retaining electrical continuity.[29] We characterize these fibers as shape memory materials and demonstrate their interesting properties
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